Row¶

Status: Stable

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

Description¶

Row[{e1, e2, ...}]

displays the ei concatenated together in a row. Row[{e1, e2, ...}, s] inserts the string s between successive elements. Strings are shown without quotes.

Examples (5)¶

Every input below was run against the current Mathilda build and its output recorded.

Basic examples (2)¶

In[1]:= Row[{"x", " = ", 5}]
Out[1]= x = 5

In[2]:= Row[{1, 2, 3}, ", "]
Out[2]= 1, 2, 3

Applications (3)¶

Elements concatenated with no separator

In[3]:= Row[{a, b, c}]
Out[3]= abc

A string inserted between successive elements

In[4]:= Row[{1, 2, 3}, ", "]
Out[4]= 1, 2, 3

Strings print without their quotes

In[5]:= Row[{"x", "=", 5}]
Out[5]= x=5

Algorithm¶

 Mathilda — NumberForm and a minimal Row.  See numberform.h for the design.

NumberForm is a PRINT WRAPPER: builtin_numberform is inert (returns NULL) so the head survives in the tree, and all display work happens here, driven by print.c which installs an active NumberFormCtx and routes every numeric leaf through numberform_render_number.

The per-number pipeline (nf_format_parts):

  1. reject non-finite; special-case zero and exact integers.
  2. extract the value's `count` significant base-10 digits + decimal
     exponent (mpfr_get_str for MPFR, "%.*e" for machine reals).
  3. decide scientific vs decimal (ScientificNotationThreshold, or the
     caller's ExponentFunction), and the displayed exponent (ExponentStep).
  4. place the digits into integer/fractional strings; {n,f} re-rounds to f
     fractional digits, plain-n drops trailing zeros.
  5. apply DigitBlock grouping, then assemble sign / point / multiplier /
     NumberFormat.

The same nf_format_parts drives the measure pass, so alignment widths and the printed output can never disagree.

Implementation notes¶

Algorithm. Row is a display wrapper like NumberForm: builtin_row (src/numberform.c) is inert (returns NULL, so the head stays in the tree) and the rendering lives in the standard printer. When print.c meets Row[{e1, e2, ...}] (first argument a List, and only outside InputForm) it sets the output-form flag and prints each element with print_standard, so strings appear without quotes; a second string argument Row[{...}, s] is emitted between successive elements as a separator. Outside that shape the literal Row[...] prints normally.

Data structures. No allocation of its own — it writes directly to stdout through the printer, toggling and restoring the global g_print_output_form flag around the element loop. Its chief internal use is as the assembler for NumberForm's NumberFormat option, where numberform_format_result_to_string renders a Row of mantissa / base / exponent pieces to an OutputForm string.

Complexity / limits. Linear in the number of elements. Row is a pure presentation head: it has no computational value and takes the list's first argument as its content, with an optional string separator. Attributes Protected.

Attributes: Protected.

References¶

See also: NumberForm

Source: src/numberform.c
Specification: docs/spec/builtins/expression-information.md
Tests: tests/test_numberform.c

Notes & additional examples¶

Notes¶

Row[{e1, e2, ...}] displays the elements concatenated left to right, with strings shown without quotes; Row[{...}, s] inserts the string s between successive elements. It is a pure presentation head with no computational value, and its main internal use is assembling a custom display for NumberForm's NumberFormat option — the pieces (mantissa, "10", exponent) are handed to the NumberFormat function, which typically wraps them in a Row.