BAP Online Manuals : Library Reference : Library by Name : is
Previous: integer
Next: isname

---

6.2.74. is

evaluates a numeric expression

SYNOPSIS

OPERATOR op(700,xfx,is).
is(Result,Term)
Result is 3+20/4

SYNTAX

is(Result,Term) (x,i)
Result is Term  (x,i)

ARGUMENTS

integer(Result) (x) numeric value of the expression Term
void(Term) (i) a Term belonging to the arithmetic domain to be evaluated

DESCRIPTION

This is a standard prolog built-in. Succeeds if Result can be matched with the result of interpreting term as an arithmetic expression. The following arithmetic expressions are legal: '+','-','*','/', and 'mod'
For these expressions operators are declared:

  op(500,yfx,"+").
  op(500,fx,"+").
  op(500,yfx,"-").
  op(500,fx,"-").
  op(400,yfx,"*").
  op(400,yfx,"/").
  op(300,xfx,"mod").

The terms may be nested.

EXAMPLE

readln(Input),		% e.g. enter "3+5", "4*6" 
fronttoken(Input,T1,,R1),
fronttoken(R1,Op,T2),
str_int(T1,I1),str_int(T2,I2),
Expr =.. [Op,I1,I2],
Sum is Expr,
write(Sum),nl.

ERRORS

No runtime errors.

LAYERS

prolog-process, client-server, object

---

BAP Online Manuals : Library Reference : Library by Name : is
Previous: integer
Next: isname