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.TH HOC 1
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.SH NAME
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hoc \- interactive floating point language
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.SH SYNOPSIS
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.B hoc
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[
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.B -e
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.I expression
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]
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[
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.I file ...
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]
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.SH DESCRIPTION
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.I Hoc
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interprets a simple language for floating point arithmetic,
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at about the level of BASIC, with C-like syntax and
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functions.
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.PP
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The named
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.I files
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are read and interpreted in order.
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If no
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.I file
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is given or if
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.I file
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is
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.L -
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.I hoc
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interprets the standard input.
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The
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.B -e
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option allows input to
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.I hoc
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to be specified on the command line, to be treated as if it appeared in a file.
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.PP
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.I Hoc
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input consists of
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.I expressions
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and
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.IR statements .
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Expressions are evaluated and their results printed.
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Statements, typically assignments and function or procedure
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definitions, produce no output unless they explicitly call
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.IR print .
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.PP
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Variable names have the usual syntax, including
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.LR _ ;
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the name
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.L _
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by itself contains the value of the last expression evaluated.
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The variables
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.BR E ,
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.BR PI ,
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.BR PHI ,
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.BR GAMMA
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and
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.B DEG
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are predefined; the last is 59.25..., degrees per radian.
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.PP
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Expressions are formed with these C-like operators, listed by
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decreasing precedence.
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.TP
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.B ^
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exponentiation
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.TP
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.B ! - ++ --
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.TP
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.B * / %
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.TP
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.B + -
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.TP
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.B > >= < <= == !=
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.TP
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.B &&
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.TP
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.B ||
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.TP
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.B = += -= *= /= %=
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.PP
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Built in functions are
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.BR abs ,
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.BR acos ,
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.BR asin ,
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.B atan
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(one argument),
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.BR cos ,
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.BR cosh ,
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.BR exp ,
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.BR int ,
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.BR log ,
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.BR log10 ,
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.BR sin ,
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.BR sinh ,
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.BR sqrt ,
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.BR tan ,
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and
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.BR tanh .
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The function
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.B read(x)
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reads a value into the variable
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.B x
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and returns 0 at EOF;
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the statement
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.B print
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prints a list of expressions that may include
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string constants such as
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\fL"hello\en"\f1.\fP
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.PP
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Control flow statements are
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.BR if - else ,
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.BR while ,
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and
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.BR for ,
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with braces for grouping.
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Newline ends a statement.
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Backslash-newline is equivalent to a space.
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.PP
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Functions and procedures are introduced by the words
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.B func
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and
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.BR proc ;
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.B return
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is used to return with a value from a function.
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.SH EXAMPLES
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.EX
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func gcd(a, b) {
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	temp = abs(a) % abs(b)
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	if(temp == 0) return abs(b)
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	return gcd(b, temp)
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}
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for(i=1; i<12; i++) print gcd(i,12)
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.EE
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.SH SOURCE
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.B /sys/src/cmd/hoc
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.SH "SEE ALSO"
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.IR bc (1),
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.IR dc (1)
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.br
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B. W. Kernighan and R. Pike,
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.I
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The Unix Programming Environment,
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Prentice-Hall, 1984
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.SH BUGS
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Error recovery is imperfect within function and procedure definitions.