From Real World Haskell:
We can immediately start entering expressions, to see what ghci will do with them. Basic arithmetic works similarly to languages like C and Python: we write expressions in infix form, where an operator appears between its operands.
Why is there no the before "infix"? This is quite a definite form of writing expressions. Is it because it is given a definition after a comma (" where an operator appears between its operands")?
Or is it because form with the will change its meaning to "a printed or typed document with blank spaces for insertion of required or requested information"?
P.S. A related question: 'in gas state' vs. 'in the gas state'.
(P.P.S. stashing a memorable usage example for myself: "Alf in pog form")