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Constraint Logic Programming: Variables and Statements

• Basic statements are constraints. \
• Constraints relate (logical) variables. \
• Such variables range over a domain (we assume floats, for now).
• Variables can be free, partially constrained, or ground (definite values).
• If Y and Z have definite values (e.g., Y=3, Z=2) then operational semantics of is simply addition and X=5
  (and can be compiled as such, if compiler can derive this info).
• If Y and Z free, then X=Y+Z stored (in some normalized form) and resolved later.
• E.g., executing the sequence:
  
  stores in memory (heap):
  Y=2
  X=2+T1
  Z=T1