FullForm¶

Status: Stable

documented, exercised by the test suite and/or worked examples, with no known limitations recorded.

Description¶

FullForm[expr]
    prints expr as its raw internal tree (heads written before arguments
    in functional form, no operator or infix sugar).
FullForm is a wrapper recognised by Print/Out; when an input evaluates
to FullForm[expr] the wrapper is consumed by the printer and does not
appear in the output.

Examples¶

No verified examples yet for this function.

Implementation notes¶

FullForm is an unevaluated display wrapper: the builtin builtin_fullform (src/print.c) returns NULL, leaving FullForm[expr] intact. Rendering is done by the printer — print_standard detects the FullForm head and calls expr_print_fullform, which writes the raw tree as head[arg, ...] with no infix/operator sugar. ToString[expr, FullForm] reuses the same path via expr_to_string_fullform.

Attributes: Protected.

Implementation status¶

Stable — documented, exercised by the test suite and/or worked examples, with no known limitations recorded.

References¶

Source: src/print.c
Specification: docs/spec/builtins/expression-information.md

Notes & additional examples¶

Worked examples¶

In[1]:= FullForm[a + b]
Out[1]= Plus[a, b]

In[1]:= FullForm[1/2]
Out[1]= Rational[1, 2]

In[1]:= FullForm[x^2 + 1]
Out[1]= Plus[1, Power[x, 2]]

In[1]:= FullForm[a/b]
Out[1]= Times[a, Power[b, -1]]

In[1]:= FullForm[x_Integer /; x > 0]
Out[1]= Condition[Pattern[x, Blank[Integer]], Greater[x, 0]]

Notes¶

FullForm reveals the raw internal tree, with every head written before its arguments and no special-cased syntax. It is the quickest way to see how surface notation like +, /, and ^ maps onto the underlying Plus/Rational/Power heads. Division is Times with a Power[_, -1] factor, so a/b is Times[a, Power[b, -1]]. It also exposes the desugaring of pattern syntax — x_Integer /; x > 0 is really Condition[Pattern[x, Blank[Integer]], Greater[x, 0]] — which is invaluable when debugging why a rule does or does not match.