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Errors

Common issues:

  • Missing full stop . at end of goal or clause.
  • Unknown operator or term syntax. Check operators and lists.
  • Non‑associative operator used in a chain. For example B1 #<=> B2 #<=> B3 needs parentheses: B1 #<=> (B2 #<=> B3).
  • Non‑linear CLP(FD) term like X*Y. Only linear arithmetic is supported.
  • Empty domain after posting constraints. Relax constraints or domains.

Use smaller examples to isolate errors and add constraints step by step.

WAM Bytecode Load Errors (experimental)

When using the WAM backend, malformed bytecode is rejected by the loader with structured errors.

Schema (representative): 

{
  "type": "BytecodeLoadError",
  "code": "OP_ARITY_MISMATCH | UNKNOWN_OPCODE | BAD_OPERAND | UNRESOLVED_LABEL | MODULE_NOT_FOUND | REGISTER_OOB | VERSION_MISMATCH",
  "message": "summary",
  "opcode": 37,
  "expectedArity": 2,
  "foundArity": 3,
  "label": "L42",
  "predicate": "m:p/2",
  "pc": 128,
  "module": "m",
  "hint": "optional guidance"
}

Examples: 

{ "type": "BytecodeLoadError", "code": "OP_ARITY_MISMATCH", "message": "opcode 37 expects 2 args, found 3", "opcode": 37, "expectedArity": 2, "foundArity": 3, "label": "L42", "predicate": "m:p/2", "pc": 57 }
{ "type": "BytecodeLoadError", "code": "UNKNOWN_OPCODE", "message": "unknown opcode 255", "opcode": 255, "pc": 3 }
{ "type": "BytecodeLoadError", "code": "UNRESOLVED_LABEL", "message": "label L_foo not defined", "label": "L_foo", "predicate": "user:q/1" }

These errors should never crash the engine; they are reported to the caller and, when the dual‑engine flag is enabled, execution can fall back to the tree‑walker.