The file format

A worksheet is a Markdown file, saved as .bbm (or .bbm.md, which Markdown viewers such as GitHub show without any setup). It reads as a tidy document in any Markdown viewer, and can be written by hand, by a script or by an AI assistant: Beermat fills in what is missing the next time it saves.

---
beermat: 1
title: Beam check
result:
  significant: 3
results: 7d4621da81717985
---

# Beam check

<!-- #t1 x=40 y=40 w=500 -->
Simply supported beam, uniform load **q** over span **L**.

```calc {#r1 x=40 y=100}
L := 6 m
q := 12 kN/m
```

```calc {#r2 x=40 y=160}
M_max := q*L^2/8 = ? kN*m   #= 54.0 kN*m
```

```plot {#p1 x=320 y=100 w=300 h=200}
x: 0 m .. L
traces:
  - y: q*x*(L - x)/2
    unit: kN*m
```

Settings

The YAML block between --- lines at the top holds the sheet’s settings. All are optional.

Regions

Region	Written as
Math	A ```calc fence, one statement per line in the linear syntax; a program’s lines are indented below its first
Text	Plain Markdown, after a <!-- #t1 … --> marker (a heading needs none)
Plot	A ```plot fence holding the plot’s settings in YAML (Plots)
Table	A ```table fence holding a Markdown table (Tables)
Picture	![alt][i1] after a <!-- #i1 … --> marker, with the picture’s data in a line [i1]: data:image/png;base64,… at the end of the file

Each region’s attributes go in braces after the fence’s name, or in the marker:

Attribute	Means
#r1	The region’s id (r math, t text, p plot, i picture). Beermat adds one if it is missing
x=40 y=100	Its position on the page, in points (1/72 inch) from the top-left of the page area
w=300 h=200	Its size, for text, plots, tables and pictures
disabled	Not worked out
decimals=2, significant=3, prefixes=false, …	The region’s own result format
name=Loads	A table’s name

Without a position, a region goes below the one before it, so a file written with no positions at all becomes one tidy column.

A page break is <!-- pagebreak y=700 -->. An area is everything between <!-- #a1 area y=720 title="Load cases" collapsed --> and <!-- /area -->.

Results

Each result is kept at the end of its line, after #=, and each error after #!:

M_max := q*L^2/8 = ? kN*m   #= 54 kN*m
y := L + 2 s                #! units do not match: L vs T

So the file reads as a finished calculation, even where Beermat isn’t installed. The statement itself is never changed: the unit you asked for stays after the ?.

The results: line in the settings is a fingerprint of everything else in the file. If anything changes outside Beermat (by hand, by a script, by a merge), the fingerprint no longer matches, and every kept result is worked out again rather than trusted. beermat check reports results that are out of date; beermat eval --write brings them up to date.

Don’t write #= lines yourself: Beermat writes them.

Order and form

• Beermat saves regions in the order they are worked out (top to bottom, then left to right), so reading the file from the top follows the calculation.
• Saving an unchanged sheet gives an identical file: the spacing and order are always the same, so changes show clearly in a diff.
• The file is UTF-8 text with LF line endings.