prolog

Module: alsdev

prolog — call a prolog term from Tcl

FORMS

prolog option ? arg arg... ?

DESCRIPTION

The prolog command provides methods for executing a prolog query in ALS Prolog from within an executing Tcl script. Option indicates how the query is expressed. The valid values for Option are :

**prolog call** module predicate ? -type arg ... ?

This version directly calls a predicate in a module with type-converted arguments. The command returns 1 if the query succeeds, or 0 if it fails. The arguments can take the following forms :

-number arg Passes arg as an integer or floating point number.

-atom arg Passes arg as an atom.

-list arg Passes arg as a list.

-var varName Passes an unbound Prolog varaible. When the Prolog variable is bound, the Tcl variable with the name varName is set to the binding.

**prolog read_call** termString ? varName ... ?

The string termString is first read as a prolog term and then called. The command returns 1 if the query succeeds, or 0 if it fails. The optional variables named by the varName arguments are set when a Prolog variable in the query string is bound. The prolog variables are matched to varNames in left-to-right depth first order.

EXAMPLES

prolog call builtins append -atom a -atom b -var x

Returns 1, and the Tcl variable x is set to {}(a,b).

prolog read_call "append(a, b, X)" x

Returns 1, and the Tcl variable x is set to {}(a,b).