1 .TH HOC 1
2 .SH NAME
3 hoc \- interactive floating point language
4 .SH SYNOPSIS
5 .B hoc
6 [
7 .I file ...
8 ]
9 [
10 .B -e
11 .I expression
12 ]
13 .SH DESCRIPTION
14 .I Hoc
15 interprets a simple language for floating point arithmetic,
16 at about the level of BASIC, with C-like syntax and
17 functions.
18 .PP
19 The named
20 .I files
21 are read and interpreted in order.
22 If no
23 .I file
24 is given or if
25 .I file
26 is
27 .L -
28 .I hoc
29 interprets the standard input.
30 The
31 .B -e
32 option allows input to
33 .I hoc
34 to be specified on the command line, to be treated as if it appeared in a file.
35 .PP
36 .I Hoc
37 input consists of
38 .I expressions
39 and
40 .IR statements .
41 Expressions are evaluated and their results printed.
42 Statements, typically assignments and function or procedure
43 definitions, produce no output unless they explicitly call
44 .IR print .
45 .PP
46 Variable names have the usual syntax, including 
47 .LR _ ;
48 the name 
49 .L _
50 by itself contains the value of the last expression evaluated.
51 The variables
52 .BR E ,
53 .BR PI ,
54 .BR PHI ,
55 .BR GAMMA
56 and
57 .B DEG 
58 are predefined; the last is 59.25..., degrees per radian.
59 .PP
60 Expressions are formed with these C-like operators, listed by
61 decreasing precedence.
62 .TP
63 .B ^
64 exponentiation
65 .TP
66 .B ! - ++ --
67 .TP
68 .B * / %
69 .TP
70 .B + -
71 .TP
72 .B > >= < <= == !=
73 .TP
74 .B &&
75 .TP
76 .B ||
77 .TP
78 .B = += -= *= /= %=
79 .PP
80 Built in functions are
81 .BR abs ,
82 .BR acos ,
83 .BR asin ,
84 .B atan
85 (one argument),
86 .BR cos ,
87 .BR cosh ,
88 .BR exp ,
89 .BR int ,
90 .BR log ,
91 .BR log10 ,
92 .BR sin ,
93 .BR sinh ,
94 .BR sqrt ,
95 .BR tan ,
96 and
97 .BR tanh .
98 The function
99 .B read(x)
100 reads a value into the variable
101 .B x
102 and returns 0 at EOF;
103 the statement
104 .B print
105 prints a list of expressions that may include
106 string constants such as
107 \fL"hello\en"\f1.\fP
108 .PP
109 Control flow statements are
110 .BR if - else ,
111 .BR while ,
112 and
113 .BR for ,
114 with braces for grouping.
115 Newline ends a statement.
116 Backslash-newline is equivalent to a space.
117 .PP
118 Functions and procedures are introduced by the words
119 .B func
120 and
121 .BR proc ;
122 .B return
123 is used to return with a value from a function.
124 .SH EXAMPLES
125 .EX
126 func gcd(a, b) {
127 	temp = abs(a) % abs(b)
128 	if(temp == 0) return abs(b)
129 	return gcd(b, temp)
130 }
131 for(i=1; i<12; i++) print gcd(i,12)
132 .EE
133 .SH SOURCE
134 .B \*9/src/cmd/hoc
135 .SH "SEE ALSO"
136 .MR bc (1) ,
137 .MR dc (1)
138 .br
139 B. W. Kernighan and R. Pike,
140 .I
141 The Unix Programming Environment,
142 Prentice-Hall, 1984
143 .SH BUGS
144 Error recovery is imperfect within function and procedure definitions.