extractBefore — Extract text before a position or boundary.
extractBefore(text, boundary) returns the text before the first matching text/pattern boundary or before a one-based numeric position. The output preserves the text input datatype and shape.
Syntax
s = extractBefore(text, boundary)Inputs
| Name | Type | Required | Default | Description |
|---|---|---|---|---|
text | Any | Yes | — | Input string array, character vector, or cell array of character vectors. |
boundary | Any | Yes | — | Text/pattern boundary or positive numeric position, scalar or the same size as text. |
Returns
| Name | Type | Description |
|---|---|---|
out | Any | Output value. |
Errors
| Identifier | When | Message |
|---|---|---|
RunMat:extractBefore:InvalidInput | The call does not contain exactly one documented text input and one boundary. | extractBefore: invalid input |
RunMat:extractBefore:InvalidBoundary | A numeric boundary is not a positive integer or a text/pattern boundary is invalid. | extractBefore: invalid boundary |
RunMat:extractBefore:SizeMismatch | A nonscalar boundary does not have the same shape as the text input. | extractBefore: boundary size must match text |
How extractBefore works
- Numeric positions are one-based structural controls. Scalar positions expand to every text element; nonscalar positions must have exactly the same shape as the text input.
- All eight built-in integer classes are read from native storage without floating-point conversion. Single and double positions must be finite positive integer values.
- String arrays, character vectors, and cell arrays of character vectors preserve their input datatype and shape. Row-wise character matrices and broader cell containers are explicit RunMat extensions.
- Missing text propagates. A text or pattern boundary that cannot be found is reported as an error by the current RunMat implementation.
- Integer, logical, complex, and resident numeric values are not accepted as text. Resident numeric positions require the RunMat extension mode and are gathered before host evaluation.
Example
Using extractBefore with coding agents
Open a RunMat example with live inputs, then ask the agent to explain how extractBefore changes the result.
Run a small extractBefore example, explain the result, then change one input and compare the output.
Related Strings functions
Transform
append · deblank · erase · eraseBetween · erasePunctuation · eraseURLs · extractAfter · extractBetween · insertAfter · insertBefore · join · lower · pad · replace · replaceBetween · reverse · split · splitlines · strcat · strip · strjoin · strjust · strrep · strsplit · strtrim · upper
Text Analytics
addDependencyDetails · addEntityDetails · addLemmaDetails · addPartOfSpeechDetails · addSentenceDetails · addTypeDetails · bagOfNgrams · bagOfWords · cosineSimilarity · doc2sequence · encode · extractFileText · extractHTMLText · fastTextWordEmbedding · findElement · getAttribute · htmlTree · ind2word · isVocabularyWord · normalizeWords · readWordEmbedding · removeLongWords · removeShortWords · removeStopWords · removeWords · stopWords · tokenDetails · tokenizedDocument · trainWordEmbedding · vaderSentimentScores · vec2word · word2ind · word2vec · wordEncoding · writeWordEmbedding
Core
blanks · char · compose · convertCharsToStrings · convertContainedStringsToChars · convertStringsToChars · genvarname · int2str · isletter · isspace · isStringScalar · isstrprop · mat2str · native2unicode · newline · num2str · sprintf · sscanf · str2double · str2num · strcmp · strcmpi · string · string.empty · strings · strlength · strncmp · strncmpi · strtok · unicode2native
Search
contains · endsWith · matches · startsWith · strfind
Pattern
digitsPattern · lettersPattern · pattern · regexpPattern · textBoundary · wildcardPattern
Open-source implementation
Unlike proprietary runtimes, every RunMat function is open-source. Read exactly how extractBefore is executed, line by line, in Rust.
- View the source for extractBefore in Rust on GitHub
- Learn how the RunMat runtime works
- Found a bug? Open an issue with a minimal reproduction.
About RunMat
RunMat is an open-source runtime that executes MATLAB-syntax code blazing on any GPU. It is licensed under the Apache 2.0 license.
- RunMat automatically optimizes your math for GPU execution on Apple, Nvidia, and AMD hardware. No code changes needed. Simulations that took hours now take minutes.
- Start running code in seconds. RunMat runs in the browser, on the desktop, or from the CLI. No license server, no IT ticket.